Viskoelastische Eigenschaften von Polyisobutylenen in verdünnten Lösungen

Zusammenfassung Die Speicher- und VerlustmodulnG undG verdünnter Lösungen (2–4%) dreier Isobutylenpolymerisate mit den Molekulargewichten 0,63, 1,29 und 11×10⁵ wurden in der Apparatur vonBirnboim undFerry über einen Frequenzbereich von 0,4–400 Hz und einen Temperaturbereich von –17,5 bis 25,0° bestimmt. Für die scharf fraktionierten Polymerisate von niederem Molekulargewicht ergab die Frequenzabhängigkeit der Moduln eine ausgezeichnete Übereinstimmung mit der Theorie vonZimm. Die aus den experimentell erhaltenen Kurven ermittelten Molekulargewichte und größten Relaxationszeiten waren von der erwarteten Größenordnung. Für das Polymerisat mit höherem Molekulargewicht entsprach die Frequenzabhängigkeit vonG undG – _s jedoch der Theorie vonRouse. Der Einfluß der hydrodynamischen Wechselwirkung in der Bewegung der Knäuelsegmente, in welchem der Unterschied zwischen den beiden Theorien besteht, erscheint als von der Größe des Molekulargewichts abhängig.

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Summary The storage and loss moduliG andG of dilute (2–4%) solutions of three polyisobutylenes of molecular weight 0.63, 1.29, and 11×10⁵ were determined in the apparatus ofBirnboim andFerry over a frequency range of 0.4 to 400 cps, and a temperature range of –17.0 to 25.0°. The sharply fractionated polymers of low molecular weight showed a frequency dependence in excellent agreement with the theory ofZimm. The experimentally determined molecular weights and terminal relaxation times were of the expected order of magnitude. The frequency dependence of the polymer of highest molecular weight, however, conformed more closely to the theory ofRouse. The influence of the hydrodynamic interaction on the motion of the coil segments, which constitutes the difference in the two theories, appears to depend on the magnitude of the molecular weight.

     

Isomerisation in the chemistry of platinacyclobutane complexes

The platinacyclobutane complexes PtCl₂L₂(C₃H₅Me)], L  pyridine, CD₃CN, or tetrahydrofuran, exist as mixtures of isomers containing P$\text{tCH}{}_2\text{CHMeC}$H₂ or P$\text{tCHMeCH}{}_2\text{CH}{}_2$ groups in rapid equilibrium. Decomposition occurs in some cases to give [PtCl₂L(CH₃CH₂CHCH₂)]. Stereospecific skeletal isomerisation also occurs in metallocyclobutanes containing the groups P$\text{tCHRCHRC}$H₂  P$\text{tCHRCH}{}_2\text{C}$HR, when R  aryl further decomposition gives ν-allylplatinum complexes.     

Spektrophotometrische Bestimmung von L-Askorbinsäure mit 2,2',5,5'-Tetra-(4-nitrophenyl)-3,3'-(3,3'-dimethoxy-4, 4'-biphenyl)-ditetrazoliumchlorid (TNBT)

Zusammenfassung Die Optimalbedingungen für die spektrophotometrische Bestimmung der L-Askorbinsäure mit TNBT wurden ermittelt. Die L-As-korbinsäure wurde in Anwesenheit eines 100fachen Überschusses folgender Stoffe bestimmt: Glukose, Fruktose, Saccharose, Wein-, Zitronen-, Oxal-, Äpfel- und Bernsteinsäure. 0,5g/ml ist die minimale Askorbinsäurekonzentration, die sich bestimmen läßt. Die rel. Standardabweichung beträgt 2,1%, der rel. Fehler 0,875%.

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Spectrophotometric assay of L. ascorbic acid with 2,2,5,5-tetra-(4-nitro-phenyl)-3, 3-(3,3-dimethoxy-4,4-biphenyl)-ditetrazolium chloride (TNBT)

Summary The optimal conditions for spectrophotometric assay of L-ascorbic acid with TNBT were determined. L-ascorbic acid was assayed in the presence of a 100 fold excess of the following substances: glucose, fructose, sucrose, tartaric acid, citric acid, oxalic acid, malic acid and succinic acid. 0.5g/ml is the minimum concentration of ascorbic acid which can be assayed. The relative standard deviation is 2.1%, the relative error 0.875%.

     

Equilibria in complexes of N-heterocyclic molecules,part XII. The reaction of hydroxide and alkoxide Ions with platinum(II) complexes of 5-nitro-1,10-phenanthroline and 2,2′-bipyridyl

Summary Bis-(5-nitro-1,10-phenanthroline)platinum(II) dichloride and diperchlorate have been prepared. The reaction between the parent cation and hydroxide ion has been studied using 1 FI n.m.r. spectroscopy and found to involve attack at the ligand. The bis-(2,2-bipyridyl)platinum(II) ion has been shown to be highly reactive towards methoxide ion. The dissociation of a 2,2-bipyridyl ligand is preceded by attack at the ligand.Part XI: R. D. Gillard, t.. A. P. Kane-Maguire and P. A. Williams,Transition Met. Chem., 2, 47 (1977).On leave from the University of Baghdad, Iraq.     

Kinetic studies in mass spectrometry—IV. The [M — Cl] reaction in substituted chlorobenzenes and the question of molecular ion isomerization.

The [M]⁺˙ → [M ? Cl]⁺ reaction in a series of m- and p-X substituted chlorobenzenes has been studied, utilizing a simple kinetic approach, comparison of metastable ion relative abundances, and by measurement of ionization and appearance potentials. All evidence obtained is consistent with rearrangement prior to cleavage in the molecular ions, in which substituent position becomes effectively randomized. These findings are related to known hydrogen randomization reactions occurring in either the molecular ion or [M ? Cl] ion of chlorobenzenes. Mechanisms involving carbon scrambling via such species as ionized benzvalenes or prismanes, or ring-opening to isomeric acyclic molecular ions in which hydrogen randomization might occur can be entertained, but mechanisms involving simple hydrogen shifts in the intact benzene ring appear less likely.     

Anwendung mikroanalytischer Methoden zur Lösung kunst- und kulturgeschichtlicher Probleme

Zusammenfassung Mit bekannten mikroanalytischen Arbeitsmethoden — Oberflächenreaktionen, Abstrichuntersuchungen mit dem Korundstäbchen, Schutzschichtreaktionen sowie dem Abdruckverfahren — lassen sich archaeometrische Probleme einer Lösung näherbringen. Die Art der Korrosion kupferhaltiger Oberflächen wurde diskutiert.

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Application of microanalytical methods to the solution of artistic- and cultural historical problems

Summary Archeometrical problems are brought closer to a solution by means of known microanalytical procedures-surface reactions, surface scraping studies with the corundum rod, protective layer reactions as well as the imprint method. A discussion of the corrosion of copper-bearing surfaces is included.

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Vortrag anläßlich der Tagung Chemische Analysen — Kunst- und Kulturwissenschaften im Reiß-Museum in Mannheim, 19.–21. September 1974.     

The surface activity of the lower homologues of n-alkylammonium chlorides in aqueous solutions. Effect of hydrophobic hydration

Summary The surface tensions of aqueous solutions ofn-alkylammonium chlorides (methyl to hexyl) have been measured at 25 °C. With methylammonium chloride the surface tension increased with concentration, whereas with ethylammonium chloride and higher homologues, the surface tension decreased with concentration. The results suggest that this transition is attributed to the effect of hydrophobic hydration. For propylammonium chloride and higher homologues, the relation between the surface tension lowering da and the concentrationC in the range of 0–10 dyne/cm, can be expressed by the equation; = AC + BC, whereA andB are constants. The surface tension coefficientB has been found to increase approximately twofold for each additional CH₂ group of alkyl chain.

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Zusammenfassung Es wurden die Oberflächenspannungen wäßriger Lösungen vonn-Alkylammoniumchloriden (Methyl- bis Hexylammoniumchloride) bei 25 °C gemessen. Für Methylammoniumchlorid nimmt die Oberflächenspannung mit der Konzentration zu, aber bei allen höheren Homologen mit der Konzentration ab. Die Ergebnisse deuten darauf hin, daß dieser Übergang durch die hydrophobe Hydration bedingt wird. Für Propylammonium-chlorid und die höheren Homologen wird die Beziehung zwischen der Erniedrigung der Oberflächenspannung und der KonzentrationC in dem Bereich von 1 bis 10 dyn/cm durch die folgende Gleichung ausgedrückt: = AC + BC (A undB sind Konstanten). Es wurde gefunden, daß B für jede zusätzliche CH₂-Gruppe etwa um den Faktor 2 größer wird.

     

Beitrag zur Kenntnis des Systems Vanadin—Chrom—Stickstoff

The System V–Cr–N has been investigated at 1100 and 1400 °C and at nitrogen pressures between 1 and 1000 atmospheres by X-ray techniques. VN and CrN on the one hand and V₂N and Cr₂N on the other are forming complete series of solid solutions. The phase field of the mononitride solid solution is dependent on nitrogen pressure and temperature conditions.

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Auszug aus der Diplomarbeit des Herrn Dipl.-Ing. Dr.W. Schebesta.     

On-line preconcentration of arsenic from water samples with an anion-exchanger column coupled to a hydride generation ICP system

Summary An on-line anion-exchange preconcentration hydride generation ICP system for the determination of total inorganic arsenic in water is described. The column was packed with strongly basic anion-exchange resin (AG 1-X8). Experimental conditions including pH of the sample solution, eluent, flow rate of eluent, oxidation states of arsenic and competing anion ions were studied. Compared with the conventional continuous hydride generation ICP, a 9.2-fold improvement in sensitivity was obtained with RSD 1–2% at 100 ng/ml. The detection limit (3) was 0.08 ng/ml. The recoveries in water samples were satisfactory. The system provides complete automation of sample loading, eluting and regenerating of the resin.On leave from Shanghai Institute of Metallurgy, Chinese Academy of Sciences, Shanghai, China 200050     

Darstellung und Reaktionen des 3-Ethinyl-2,4-diformyl-pentandials

Preparation and physical and chemical properties of 3-ethinyl-2,4-diformyl-pentandial (3 a) and its salts are described.3 a contains 2 malonaldehyde groups. Starting from3 a, 4H-pyranes, 4H-dihydropyridines, dipyrazoles, diisoxazoles, bisdiazepines and vinamidine derivates are obtained.

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